include/linux/swapops.h

   1 #ifndef _LINUX_SWAPOPS_H
   2 #define _LINUX_SWAPOPS_H
   3
   4 #include <linux/radix-tree.h>
   5 #include <linux/bug.h>
   6
   7 /*
   8  * swapcache pages are stored in the swapper_space radix tree.  We want to
   9  * get good packing density in that tree, so the index should be dense in
  10  * the low-order bits.
  11  *
  12  * We arrange the `type' and `offset' fields so that `type' is at the seven
  13  * high-order bits of the swp_entry_t and `offset' is right-aligned in the
  14  * remaining bits.  Although `type' itself needs only five bits, we allow for
  15  * shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry().
  16  *
  17  * swp_entry_t's are *never* stored anywhere in their arch-dependent format.
  18  */
  19 #define SWP_TYPE_SHIFT(e)       ((sizeof(e.val) * 8) - \
  20                         (MAX_SWAPFILES_SHIFT + RADIX_TREE_EXCEPTIONAL_SHIFT))
  21 #define SWP_OFFSET_MASK(e)      ((1UL << SWP_TYPE_SHIFT(e)) - 1)
  22
  23 /*
  24  * Store a type+offset into a swp_entry_t in an arch-independent format
  25  */
  26 static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
  27 {
  28         swp_entry_t ret;
  29
  30         ret.val = (type << SWP_TYPE_SHIFT(ret)) |
  31                         (offset & SWP_OFFSET_MASK(ret));
  32         return ret;
  33 }
  34
  35 /*
  36  * Extract the `type' field from a swp_entry_t.  The swp_entry_t is in
  37  * arch-independent format
  38  */
  39 static inline unsigned swp_type(swp_entry_t entry)
  40 {
  41         return (entry.val >> SWP_TYPE_SHIFT(entry));
  42 }
  43
  44 /*
  45  * Extract the `offset' field from a swp_entry_t.  The swp_entry_t is in
  46  * arch-independent format
  47  */
  48 static inline pgoff_t swp_offset(swp_entry_t entry)
  49 {
  50         return entry.val & SWP_OFFSET_MASK(entry);
  51 }
  52
  53 #ifdef CONFIG_MMU
  54 /* check whether a pte points to a swap entry */
  55 static inline int is_swap_pte(pte_t pte)
  56 {
  57         return !pte_none(pte) && !pte_present(pte) && !pte_file(pte);
  58 }
  59 #endif
  60
  61 /*
  62  * Convert the arch-dependent pte representation of a swp_entry_t into an
  63  * arch-independent swp_entry_t.
  64  */
  65 static inline swp_entry_t pte_to_swp_entry(pte_t pte)
  66 {
  67         swp_entry_t arch_entry;
  68
  69         BUG_ON(pte_file(pte));
  70         arch_entry = __pte_to_swp_entry(pte);
  71         return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
  72 }
  73
  74 /*
  75  * Convert the arch-independent representation of a swp_entry_t into the
  76  * arch-dependent pte representation.
  77  */
  78 static inline pte_t swp_entry_to_pte(swp_entry_t entry)
  79 {
  80         swp_entry_t arch_entry;
  81
  82         arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
  83         BUG_ON(pte_file(__swp_entry_to_pte(arch_entry)));
  84         return __swp_entry_to_pte(arch_entry);
  85 }
  86
  87 static inline swp_entry_t radix_to_swp_entry(void *arg)
  88 {
  89         swp_entry_t entry;
  90
  91         entry.val = (unsigned long)arg >> RADIX_TREE_EXCEPTIONAL_SHIFT;
  92         return entry;
  93 }
  94
  95 static inline void *swp_to_radix_entry(swp_entry_t entry)
  96 {
  97         unsigned long value;
  98
  99         value = entry.val << RADIX_TREE_EXCEPTIONAL_SHIFT;
 100         return (void *)(value | RADIX_TREE_EXCEPTIONAL_ENTRY);
 101 }
 102
 103 #ifdef CONFIG_MIGRATION
 104 static inline swp_entry_t make_migration_entry(struct page *page, int write)
 105 {
 106         BUG_ON(!PageLocked(page));
 107         return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
 108                         page_to_pfn(page));
 109 }
 110
 111 static inline int is_migration_entry(swp_entry_t entry)
 112 {
 113         return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
 114                         swp_type(entry) == SWP_MIGRATION_WRITE);
 115 }
 116
 117 static inline int is_write_migration_entry(swp_entry_t entry)
 118 {
 119         return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
 120 }
 121
 122 static inline struct page *migration_entry_to_page(swp_entry_t entry)
 123 {
 124         struct page *p = pfn_to_page(swp_offset(entry));
 125         /*
 126          * Any use of migration entries may only occur while the
 127          * corresponding page is locked
 128          */
 129         BUG_ON(!PageLocked(p));
 130         return p;
 131 }
 132
 133 static inline void make_migration_entry_read(swp_entry_t *entry)
 134 {
 135         *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
 136 }
 137
 138 extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 139                                         unsigned long address);
 140 #else
 141
 142 #define make_migration_entry(page, write) swp_entry(0, 0)
 143 static inline int is_migration_entry(swp_entry_t swp)
 144 {
 145         return 0;
 146 }
 147 #define migration_entry_to_page(swp) NULL
 148 static inline void make_migration_entry_read(swp_entry_t *entryp) { }
 149 static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 150                                          unsigned long address) { }
 151 static inline int is_write_migration_entry(swp_entry_t entry)
 152 {
 153         return 0;
 154 }
 155
 156 #endif
 157
 158 #ifdef CONFIG_MEMORY_FAILURE
 159 /*
 160  * Support for hardware poisoned pages
 161  */
 162 static inline swp_entry_t make_hwpoison_entry(struct page *page)
 163 {
 164         BUG_ON(!PageLocked(page));
 165         return swp_entry(SWP_HWPOISON, page_to_pfn(page));
 166 }
 167
 168 static inline int is_hwpoison_entry(swp_entry_t entry)
 169 {
 170         return swp_type(entry) == SWP_HWPOISON;
 171 }
 172 #else
 173
 174 static inline swp_entry_t make_hwpoison_entry(struct page *page)
 175 {
 176         return swp_entry(0, 0);
 177 }
 178
 179 static inline int is_hwpoison_entry(swp_entry_t swp)
 180 {
 181         return 0;
 182 }
 183 #endif
 184
 185 #if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION)
 186 static inline int non_swap_entry(swp_entry_t entry)
 187 {
 188         return swp_type(entry) >= MAX_SWAPFILES;
 189 }
 190 #else
 191 static inline int non_swap_entry(swp_entry_t entry)
 192 {
 193         return 0;
 194 }
 195 #endif
 196
 197 #endif /* _LINUX_SWAPOPS_H */